This invention relates to fluid pressurizing devices for balloon catheters or the like, and more particularly relates to an improved device for actuating a screw plunger and monitoring the resulting fluid pressurization.
Fluid pressurization devices adapted for selectively applying and relieving a measured pressure on a closed volume of fluid have been developed for use in inflation and deflation of a balloon catheter used in angioplasty balloon procedures interiorly of blood vessels, or other types of balloon catheterization procedures. For example, U.S. Pat. No. 4,838,864 discloses a syringe device which inflates and deflates a catheterized balloon. The device uses a manually-operated screw plunger to achieve or maintain specific balloon pressure, and the pressure is monitored using an associated pressure gauge. Improved syringing and pressurization control is also described in U.S. Pat. Nos. 5,168,757 and 5,713,242, both of which are incorporated herein in their entirety by reference. The ""757 and ""242 patents disclose quick release mechanisms which enable rapid advancement of a threaded screw plunger and alternatively allow threaded engagement with the screw plunger to achieve precise control during final pressurization of a balloon catheter.
A cross-sectional view of the device which is disclosed in U.S. Pat. No. 5,713,242 is shown generally in FIG. 1 (FIG. 1 corresponds to FIG. 2 of the ""242 patent). As shown, the device 10 provides that a piston 12 is engaged with a plunger 14 inside a fluid displacement chamber 16 provided in a housing 18. The design of the device 10 (see specifically walls 20 and 22 of the housing 18) is such that the piston 12 must be front-loaded into the fluid displacement chamber 16. More specifically, the piston 12 is slid into the front 24 of the fluid displacement chamber 16, from left-to-right in FIG. 1, and then a fitting 26 and a clamping cover 28 is engaged and sealed with the end of the housing 18 to close off the end 24 of the fluid displacement chamber 16. It is important to provide that the chamber 16 is sealed because the chamber 16 becomes pressurized when the device 10 is in use. The fitting 26 carries a gauge 30 which is configured to monitor the pressure of the chamber 16 while the device 10 is used. Because the clamping cover 28 and fitting 26 are parts which are distinct from the housing 18, the parts must be manually handled, which complicates the assembly process and consumes labor. Additionally, these extra parts, being located at the distal end (i.e. the end where the clamping cover 28 and fitting 26 are located) of the device 10, may obstruct the view of a physician who is attempting to purge the device by getting all the air bubbles out of the chamber 16.
The present invention is an improvement on this prior art design as it involves a construction which permits the unit to be assembled entirely from the rear. Thus, the main housing, including the forward portion that receives and supports the pressure gauge can be fabricated as a single, integral component. Additionally, the design provides that many of the parts are universal such that they are compatible with devices of different sizes.
An object of an embodiment of the present invention is to provide an improved device for actuating a screw plunger and monitoring the resulting fluid pressurization.
Another object of an embodiment of the present invention is to provide an improved structure and process for assembling a fluid displacement device.
Still another object of an embodiment of the present invention is to provide a fluid displacement device which is relatively easy to assemble.
Another object of an embodiment of the present invention is to provide a fluid displacement device which includes a housing which directly receives a pressure gauge, without requiring an extra fitting.
Still yet another object of an embodiment of the present invention is to provide a fluid displacement device which is configured to withstand intense chamber pressure during use.
Another object of an embodiment of the present invention is to provide a fluid displacement device which includes a carrier member that is configured to provide an audible indication when it is properly and fully installed on the device.
Still yet another object of an embodiment of the present invention is to provide a fluid displacement device which provides high visibility at a distal end, thereby allowing a user to eliminate any air bubbles while priming the device for use.
Still yet another object of an embodiment of the present invention is to provide a fluid displacement device which is designed such that many of the parts are universal such that they are compatible with devices of different sizes.
Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides an actuating mechanism for rapidly and selectively moving a threaded screw and nut member combination into or out of threaded engagement, particularly for use of the screw as a control fluid plunger to pressurize balloon catheters, or the like. The mechanism includes a housing and a threaded screw structure slidably displaceable through the housing. A nut member having partial threads is selectively engageable and disengageable with the threaded screw structure. The nut member is configured to enable selective movement of the nut member relative to the screw structure to provide selective threaded engageability of the partial threads with the screw structure. At least a portion of the nut member is disposed in a carrier member, and the carrier member is disposed generally in the housing.
The mechanism includes a plurality of link members, at least one of which is engaged with the nut member. Link structure is configured to couple the carrier member to the link members, thereby providing that the nut member and link members are pivotable relative to the carrier member. Preferably, the carrier member is disposed proximate one end of the housing, and an opposite end of the housing is configured to receive a pressure gauge directly into a threaded bore. The carrier member is preferably configured to be retainably engaged with the housing via a bayonet arrangement, such as a quarter-turn bayonet arrangement. Additionally, preferably the carrier member is configured to provide an audible indication when it is, in fact, properly and fully installed. The audible indication may be provided by a latching finger on the carrier member which engages corresponding structure on the housing. Preferably, engagement of the latching finger on the carrier member with the retaining structure on the housing provides that the carrier member does not readily rotate (i.e. counter rotation) relative to the housing.
Preferably, the nut member is bifurcated to provide a pair of opposingly spaced mounting portions extending from the partially threaded portion of the nut member. The mounting portions are effectively coupled to the housing by a pair of adjacently arranged link members which are separately coupled to the respective mounting portions and are disposed therebetween while being operable in tandem to guide translating motion of the nut member. The nut member preferably moves in a plane in a diminishing curved path in traveling between an engaged position and a disengaged position.
Preferably, the carrier member is received in a bore in the housing and a radius of the bore is larger than a distance from a center line of the threaded screw structure to the link structure which engages the carrier member. The carrier member provides that the device is assembled by rear loading the piston into the fluid displacement chamber provided in the housing.
Another aspect of the present invention provides a method of assembling an actuating mechanism. The assembly method includes engaging a hose with a housing, engaging a gauge with the housing, placing a sealing member on a piston, sliding the piston into the housing from the back end of the housing, sliding a carrier member into the housing through a back end of the housing, rotating the carrier member thereby providing that the carrier member generally locks in place with respect to the housing, installing link members in a nut member, placing the nut member generally into the carrier member, engaging a pivot pin with the carrier member and the link members, sliding a plunger into the back end of the housing through the nut member and carrier member, and engaging the plunger with the piston.
As mentioned above, this permits the housing to be fabricated, as by molding, as a single component. This not only reduces the cost of the components and molds, but facilitates assembly, thereby reducing labor costs, all of which is achieved with the structure illustrated and described hereinafter.